Bringing the Pediatric Endocrine Spanish Speaking Community Together: First Virtual Pediatric Endocrine Meeting in Low- and Middle-Income Countries in Central and South America

BACKGROUND

Pediatric endocrinology is a specialty that is struggling worldwide to maintain adequately trained professionals. Pediatric endocrine care in Central America and Caribbean countries is often performed by pediatricians or adult endocrinologists due to the limited number of pediatric endocrinologists. These health care providers are seldom members of endocrine societies and frequently lack formal training in the field.

OBJECTIVE

In this study, we describe the scope of a virtual conference in pediatric endocrinology and diabetes targeted to low- and middle-income countries to provide equal opportunities for access to medical education for health care professionals.

METHODS

The virtual conference was sponsored by the Pediatric Endocrine Society (North America), Asociación Costarricense de Endocrinología (previously, Asociación Nacional Pro Estudio de la Diabetes, Endocrinología y Metabolismo), and Asociacion Centroamericana y del Caribe de Endocrinologia Pediátrica. The conference was free to participants and comprised 23 sessions that were either synchronous with ability for real-time interactive sessions or asynchronous sessions, where content was available online to access at their convenience. Topics included idiopathic short stature, polycystic ovarian syndrome, diabetes mellitus, telemedicine, Turner syndrome, congenital adrenal hyperplasia, obesity, central precocious puberty, and subclinical hypothyroidism. The participants were asked to evaluate the conference after its completion with a questionnaire.

RESULTS

A total of 8 speakers from Spain, Canada, Costa Rica, and the United States delivered the virtual event to 668 health care professionals from Guatemala, Venezuela, Dominican Republic, Costa Rica, Ecuador, Peru, Uruguay, Mexico, Honduras, Argentina, the United States, Bolivia, Chile, Panama, El Salvador, Nicaragua, Paraguay, Belize, Spain, and Colombia. Name, profession, and country were fully disclosed by 410 (61.4%) of the 668 health care professionals. The profession or level of training of participants were as follows: pediatric endocrinologists (n=129, 19.3%), pediatricians (n=116, 17.4%), general practitioners (n=77, 11.5%), adult endocrinologists (n=34, 5.1%), medical students (n=23, 3.4%), residents in various specialties (n=14, 2.1%), and others (n=17, 2.6%). A total of 23 sessions were offered, most of which were bilingual (Spanish and English). Feedback from the evaluation questionnaire indicated that the content of the conference was very relevant to the participants' professional practice. Additionally, the participants reported that they were very satisfied with the organization, the web-based platform, and the sessions of the conference.

CONCLUSIONS

Lack of accessibility to the latest and cutting-edge medical education in pediatric endocrinology and diabetes for medical professionals from low- and middle-income countries can be overcome with a virtual conference. Online availability, low cost, and easy-to-use technology were well received from the participants, who were overall very satisfied by the quality and the relevance of the sessions to their professional practice.

Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement

Despite the high prevalence of performance-enhancing drug (PED) use, media attention has focused almost entirely on PED use by elite athletes to illicitly gain a competitive advantage in sports, and not on the health risks of PEDs. There is a widespread misperception that PED use is safe or that adverse effects are manageable. In reality, the vast majority of PED users are not athletes but rather nonathlete weightlifters, and the adverse health effects of PED use are greatly underappreciated. This scientific statement synthesizes available information on the medical consequences of PED use, identifies gaps in knowledge, and aims to focus the attention of the medical community and policymakers on PED use as an important public health problem. PED users frequently consume highly supraphysiologic doses of PEDs, combine them with other PEDs and/or other classical drugs of abuse, and display additional associated risk factors. PED use has been linked to an increased risk of death and a wide variety of cardiovascular, psychiatric, metabolic, endocrine, neurologic, infectious, hepatic, renal, and musculoskeletal disorders. Because randomized trials cannot ethically duplicate the large doses of PEDs and the many factors associated with PED use, we need observational studies to collect valid outcome data on the health risks associated with PEDs. In addition, we need studies regarding the prevalence of PED use, the mechanisms by which PEDs exert their adverse health effects, and the interactive effects of PEDs with sports injuries and other high-risk behaviors. We also need randomized trials to assess therapeutic interventions for treating the adverse effects of PEDs, such as the anabolic-androgen steroid withdrawal syndrome. Finally, we need to raise public awareness of the serious health consequences of PEDs.

Biological assessment of abnormal genitalia

Biological assessment of abnormal genitalia is based on an ordered sequence of endocrine and genetic investigations that are predicated on knowledge obtained from a suitable history and detailed examination of the external genital anatomy. Investigations are particularly relevant in 46,XY DSD where the diagnostic yield is less successful than in the 46,XX counterpart. Advantage should be taken of spontaneous activity of the pituitary-gonadal axis in early infancy rendering measurements of gonadotrophins and sex steroids by sensitive, validated assays key to assessing testicular function. Allied measurement of serum anti-Müllerian hormone completes a comprehensive testis profile of Leydig and Sertoli cell function. Genetic assessment is dominated by analysis of a plethora of genes that attempts to delineate a cause for gonadal dysgenesis. In essence, this is successful in up to 20% of cases from analysis of SRY and SF1 (NR5A1) genes. In contrast, gene mutation analysis is highly successful in 46,XY DSD due to defects in androgen synthesis or action. The era of next generation sequencing is increasingly being applied to investigate complex medical conditions of unknown cause, including DSD. The challenge for health professionals will lie in integrating vast amounts of genetic information with phenotypes and counselling families appropriately. How tissues respond to hormones is apposite to assessing the range of genital phenotypes that characterise DSD, particularly for syndromes associated with androgen resistance. In vitro methods are available to undertake quantitative and qualitative analysis of hormone action. The in vivo equivalent is some assessment of the degree of under-masculinisation in the male, such as an external masculinisation score, and measurement of the ano-genital distance. This anthropometric marker is effectively a postnatal readout of the effects of prenatal androgens acting during the masculinisation programming window. For investigation of the newborn with abnormal genitalia, a pragmatic approach can be taken to guide the clinician using appropriate algorithms.

Optimizing potential for fertility: fertility considerations for the pediatrician

Whether for the prepubertal or pubertal child, the goal of fertility preservation is to obtain cells or tissues to be used to produce future children. For the prepubertal child, preservation efforts involve germ cells, earlier forms of sperm, and immature follicles, rather than mature spermatozoa or follicles. Options for prepubertal children include for boys freezing testicular tissue and extracting testicular sperm or for girls obtaining ovarian cortical or follicular tissue for storage. These procedures involve extraction and storage of immature gametes for subsequent in vitro maturation, although attempts for sperm currently involve only animal studies. For adolescent subjects who have sufficient gonadal development and reserve, sperm, oocytes, and ovarian cortex can be retrieved as among adults.

Fertility in men with Klinefleter syndrome

Klinefelter syndrome is an important cause of infertility among men. Although early development of the testes may appear normal, there is profound loss of germ cells during early-to-mid pubertal maturation. Spermatogenesis may be preserved in a small percent of tubules and these tubules may be available to artificial reproductive techniques for the retrieval and subsequent in vitro fertilization of extracted ova. Ethical and legal issues including risk-benefit consideration must be evaluated before implementing fertility preservation procedures in minors.

Clinical variability and novel neurodevelopmental findings in 49, XXXXY syndrome

49, XXXXY is a rare chromosomal syndrome due to double nondisjunction of the replicating X chromosome. Considered a severe variant of XXY or Klinefelter syndrome, boys with this chromosome constitution are assumed to have severe mental retardation (MR) in addition to craniofacial, genital, endocrine, and heart abnormalities. Here, we present a multidisciplinary analysis including the clinical and neurobehavioral aspects of this condition in 20 boys with 49, XXXXY who share a common phenotype and neurobehavioral profile. The phenotypic presentation of the boys with 49, XXXXY shares some characteristics with 47, XXY, but there are also other unique and distinctive features. Previously unappreciated intact nonverbal skills are evident in conjunction with moderate to severe developmental dyspraxia. Variability in clinical and cognitive functioning may reflect skewed X inactivation, mosaicism, or other factors that warrant further investigation.

Optimizing potential for fertility: fertility preservation considerations for the pediatric endocrinologist

Whether for the prepubertal or pubertal child, the goal of fertility preservation is to obtain cells or tissues to be used to produce future children. For the prepubertal child, preservation efforts involve germ cells, earlier forms of sperm, and immature follicles, rather than mature spermatozoa or follicles. Options for prepubertal children include for boys freezing testicular tissue and extracting testicular sperm or for girls obtaining ovarian cortical or follicular tissue for storage. These procedures involve extraction and storage of immature gametes for subsequent in vitro maturation, although attempts for sperm currently involve only animal studies. For adolescent subjects who have sufficient gonadal development and reserve, sperm, oocytes, and ovarian cortex can be retrieved as among adults.

Consensus statement on the use of gonadotropin-releasing hormone analogs in children

OBJECTIVE

Gonadotropin-releasing hormone analogs revolutionized the treatment of central precocious puberty. However, questions remain regarding their optimal use in central precocious puberty and other conditions. The Lawson Wilkins Pediatric Endocrine Society and the European Society for Pediatric Endocrinology convened a consensus conference to review the clinical use of gonadotropin-releasing hormone analogs in children and adolescents.

PARTICIPANTS

When selecting the 30 participants, consideration was given to equal representation from North America (United States and Canada) and Europe, an equal male/female ratio, and a balanced spectrum of professional seniority and expertise.

EVIDENCE

Preference was given to articles written in English with long-term outcome data. The US Public Health grading system was used to grade evidence and rate the strength of conclusions. When evidence was insufficient, conclusions were based on expert opinion.

CONSENSUS PROCESS

Participants were put into working groups with assigned topics and specific questions. Written materials were prepared and distributed before the conference, revised on the basis of input during the meeting, and presented to the full assembly for final review. If consensus could not be reached, conclusions were based on majority vote. All participants approved the final statement.

CONCLUSIONS

The efficacy of gonadotropin-releasing hormone analogs in increasing adult height is undisputed only in early-onset (girls <6 years old) central precocious puberty. Other key areas, such as the psychosocial effects of central precocious puberty and their alteration by gonadotropin-releasing hormone analogs, need additional study. Few controlled prospective studies have been performed with gonadotropin-releasing hormone analogs in children, and many conclusions rely in part on collective expert opinion. The conference did not endorse commonly voiced concerns regarding the use of gonadotropin-releasing hormone analogs, such as promotion of weight gain or long-term diminution of bone mineral density. Use of gonadotropin-releasing hormone analogs for conditions other than central precocious puberty requires additional investigation and cannot be suggested routinely.

Management of the child born small for gestational age through to adulthood: a consensus statement of the International Societies of Pediatric Endocrinology and the Growth Hormone Research Society

OBJECTIVE

Low birth weight remains a major cause of morbidity and mortality in early infancy and childhood. It is associated with an increased risk of health problems later in life, particularly coronary heart disease and stroke. A meeting was convened to identify the key health issues facing a child born small for gestational age (SGA) and to propose management strategies.

PARTICIPANTS

There were 42 participants chosen for their expertise in obstetrics, peri- and neonatal medicine, pediatrics, pediatric and adult endocrinology, epidemiology, and pharmacology.

EVIDENCE

Written materials were exchanged, reviewed, revised, and then made available to all. This formed the basis for discussions at the meeting. Where published data were not available or adequate, discussion was based on expert clinical opinions.

CONSENSUS PROCESS

Each set of questions was considered by all and then discussed in plenary sessions with consensus and unresolved issues identified. The consensus statement was prepared in plenary sessions and then edited by the group chairs and shared with all participants.

CONCLUSIONS

The diagnosis of SGA should be based on accurate anthropometry at birth including weight, length, and head circumference. We recommend early surveillance in a growth clinic for those without catch-up. Early neurodevelopment evaluation and interventions are warranted in at-risk children. Endocrine and metabolic disturbances in the SGA child are recognized but infrequent. For the 10% who lack catch-up, GH treatment can increase linear growth. Early intervention with GH for those with severe growth retardation (height sd score, <-2.5; age, 2-4 yr) should be considered at a dose of 35-70 microg/kg x d. Long-term surveillance of treated patients is essential. The associations at a population level between low birth weight, including SGA, and coronary heart disease and stroke in later life are recognized, but there is inadequate evidence to recommend routine health surveillance of all adults born SGA outside of normal clinical practice.

Pharmacokinetic studies of recombinant human insulin-like growth factor I (rhIGF-I)/rhIGF-binding protein-3 complex administered to patients with growth hormone insensitivity syndrome

CONTEXT

GH insensitivity syndrome (GHIS), Laron syndrome, is characterized by severe short stature, high serum GH levels, and very low serum IGF-I and IGF-binding protein-3 (IGFBP-3) levels associated with a genetic defect of the GH receptor. Recombinant human (rh) IGF-I treatment at doses of 80-120 microg/kg given sc twice daily is effective in promoting growth in these patients. We have investigated a newly developed drug, rhIGF-I/rhIGFBP-3, a 1:1 molar complex of rhIGF-I and rhIGFBP-3.

OBJECTIVES

The objectives of the study were to determine IGF-I pharmacokinetics after the administration of rhIGF-I/rhIGFBP-3 in adolescents with GHIS and to evaluate its safety and tolerability.

DESIGN

This was an open-label clinical study.

SETTING

The study was conducted in a general pediatric ward of a university teaching hospital.

PARTICIPANTS

Four patients (one female and three males; mean age, 14.9 yr; mean height sd score, -4.9) with confirmed molecular diagnosis of GHIS agreed to participate in the study.

INTERVENTION

rhIGF-I/rhIGFBP-3 was administered in a single sc injection at 0.5 and 1.0 mg/kg.dose (equivalent to 100 and 200 microg/kg rhIGF-I) after breakfast with a 2-d interval between doses.

RESULTS

IGF-I levels reached a maximum between 19 +/- 8.3 and 15 +/- 6.2 h for the low and high doses, respectively. The circulating IGF-I levels obtained with the low and high doses were similar, although a discrete dose-dependent increase in circulating IGF-I levels was observed. The IGF-I half-life in four subjects after a dose of 0.5 mg/kg rhIGF-I/rhIGFBP-3 was estimated to be 21+/- 4 h. There were no acute adverse events reported, and all blood glucose measurements were normal.

CONCLUSION

These data demonstrated that the rhIGF-I/rhIGFBP-3 complex was effective in increasing levels of circulating total and free IGF-I into the normal range for a 24-h period after a single sc administration in patients with GHIS, and that administration of rhIGF-I/rhIGFBP-3 was safe and well tolerated.

Klinefelter syndrome: Expanding the phenotype and identifying new research directions

PURPOSE

The purpose of this study is to summarize new data on etiology and clinical features of Klinefelter syndrome in order to derive research priorities.

METHODS

This study was conducted using critical reviews of selective topics, emphasizing less well-recognized clinical findings.

RESULTS AND CONCLUSIONS

The phenotype of the prototypic 47,XXY case is well recognized: seminiferous tubule dysgenesis and androgen deficiency. Less well appreciated is the varied expressivity of 47,XXY Klinefelter syndrome, in particular neurological/cognitive perturbations like language and behavioral problems. Effective therapies are available. Reproductive technologies allow 47,XXY men to sire offspring through intracytoplasmic sperm injection (ICSI); however, genetic counseling is complex and success is low. Behavioral and expressive language difficulties are amenable to treatment by androgen therapy and psychological help. Early treatment may be imperative for optimal outcome.

Discordant phenotypes and 45,X/46,X,idic(Y)

Mosaicism introduces wide variability into the clinical expression of numerical and unbalanced structural chromosomal abnormalities. The phenotypic range of variability of 45,X/46,XY mosaicism extends from Turner syndrome to mixed gonadal dysgenesis to normal males. The specific phenotype is primarily dependent on the chromosomal constitution of the developing gonad. Similar phenotypic variability is observed with mosaicism for 45,X and a second cell line with an abnormal sex chromosome. This report describes a patient with Turner syndrome and a patient with mixed gonadal dysgenesis who have identical karyotypes, namely 45,X/46,X,idic(Y)(p11.2). While mosaicism alone might have accounted for the phenotypic differences, by PCR analysis the Turner syndrome patient was SRY and ZFY negative and the mixed gonadal dysgenesis patient was SRY and ZFY positive.

Partial growth-hormone insensitivity: the role of growth-hormone receptor mutations in idiopathic short stature

Mutations in the GHR locus may play a role in the cause of idiopathic short stature (ISS) by impairing growth-hormone (GH) receptor (GHR) function. At one extreme, mutations that nullify the function of the GH receptor are linked to complete GH insensitivity syndrome, or Laron syndrome, and we hypothesized that less-disruptive mutations could contribute to partial GH insensitivity syndrome. Low levels of GH binding protein may indicate mutations in the extracellular domain of the receptor, and by focusing on 14 children with ISS who had low GH binding protein and insulin-like growth factor I levels, we found three heterozygotes and one compound heterozygote for mutations in the extracellular domain of the receptor. We have since extended our study to a broader spectrum of patients, adding 76 patients with ISS who were treated with GH in a phase II study of the safety and efficacy of recombinant human GH in ISS and also adding 10 patients who were ascertained as having ISS by pediatric endocrinologists in private practice. The GHR gene has thus been analyzed in 100 patients with ISS, eight of whom were found to carry mutations: four in our original study and four with normal or elevated levels of GH binding protein. The latter group consists of three carriers of heterozygous extracellular domain mutations and one carrier of a heterozygous intracellular domain mutation. Family data suggest that the carriers of these mutations have a range of phenotypes, supporting our hypothesis that the expression of these heterozygous mutations as partial GH insensitivity syndrome depends on the genetic makeup of the person.

Role of steroidogenic acute regulatory protein in adrenal and gonadal steroidogenesis

Congenital lipoid adrenal hyperplasia is an autosomal recessive disorder that is characterized by impaired synthesis of all adrenal and gonadal steroid hormones. In three unrelated individuals with this disorder, steroidogenic acute regulatory protein, which enhances the mitochondrial conversion of cholesterol into pregnenolone, was mutated and nonfunctional, providing genetic evidence that this protein is indispensable normal adrenal and gonadal steroidogenesis.

Prediction of lactate threshold (LT) and fixed blood lactate concentrations (FBLC) from 3200-m running performance in women

The present study evaluated the accuracy of predicting velocity and oxygen consumption (VO2) at the LT lactate threshold and FBLC fixed blood lactate concentrations from a 3200-m time trial in women. Forty-four women (mean age = 31.1 yrs, mean ht = 164.9 cm, mean wt = 65.0 kg) completed a treadmill protocol for the determination of LT and FBLC and a 3200-m time trial. Velocity and VO2 values at LT, FBLC of 2.0 2.5, and 4.0 mM, and peak were determined. Mean VO2 and velocity ranged from 27.8 +/- 10.8 ml/kg.min-1 at LT to 42.5 ml/kg.min-1 at peak and from 129.8 +/- 44.0 m.min-1 at LT to 187.0 +/- 52.4 m.min-1 at peak, respectively. Results indicated that a 3200-m time trial (mean time = 20.6 +/- 6.6 min) was a good predictor of VO2 and velocity at LT, FBLC, and peak. Correlation coefficients (using a quadratic model) for velocity ranged from R = 0.96 to R = 0.98 with SEE ranging from 9.0 to 13.1 m.min-1. Correlation coefficients for VO2 ranged from R = 0.94 to R = 0.96 with SEE ranging from 2.8 to 3.6 ml/kg.min. The validity of these regression equations was examined in 13 women who completed a 12-month running program (VO2 LT, VO2 at FBLC of 2.0, 2.5 and 4.0 mM, and VO2 peak increased by 34.7, 19.9, 16.9, 11.9, and 5.4%, respectively, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Percentages of maximal heart rate, heart rate reserve and VO2max for determining endurance training intensity in male runners

The use of 60%-95% of maximal heart rate (HR), heart rate reserve (HRR) and VO2max as exercise training intensities was examined in male runners, and these intensities were related to VO2 observed at the lactate threshold (LT) and fixed blood lactate concentrations (FBLC) of 2.0, 2.5, and 4.0 mM. Thirty-one subjects (means age = 29.9 +/- 9.1 yrs; means ht = 177.3 +/- 8.2 cm; means wt = 69.2 +/- 9.9 kg) completed a level running treadmill protocol. The mean values at LT, FBLC of 2.0, 2.5, 4.0 mM and max for VO2 were 52.7, 56.4, 58.0, 61.2 and 63.5 ml/kg.min -1, respectively: for velocity they were 237.4, 252.2, 260.6, 274.4 and 286.5 m/min, respectively; and for HR were 165.7, 172.7, 176.5, 182.3 and 187.4 bts/min, respectively. The majority of subjects were not above LT (N = 20), until an intensity of 90% HR max was attained. At 95% HR max the majority of subjects were above 2.0 mM (N = 23) and 2.5 mM (N = 17) but below 4.0 mM (N = 26). For HRR, 85% HRR was necessary for the majority of subjects to be above LT (N = 20), 90% HRR resulted in the majority of subjects being above 2.0 mM (N = 19), while 95% HRR was required for the majority of subjects to be above 2.5 mM (N = 23). At 95% HRR 14 subjects were above 4.0 mM. For % VO2max, the intensities required for the majority of subjects to be above LT, FBLC of 2.0, and 2.5 mM were 90%, 95% and 95% VO2max, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Primary cortisol resistance presenting as isosexual precocity

Primary cortisol resistance (PCR) is a rare cause of hypercortisolism and usually does not produce clinical manifestations. This report describes primary cortisol resistance in a boy with isosexual precocity. A 6 7/12-yr-old boy had Tanner stage 3 pubic hair, accelerated linear growth, and advanced bone age (10 yr), but normal (for age) tests. There were no features of glucocorticoid excess. Serum androstenedione and dehydroepiandrosterone concentrations were 4.7 +/- 0.3 nmol/L (mean +/- SEM of four measurements; normal less than 1.2) and 13.5 nmol/L (single measurement; normal, 1.0-2.2), respectively. The serum testosterone concentration was 0.9 nmol/L (normal, less than 0.7), and FSH and LH were normal. Serum cortisol concentrations were 1590 +/- 110 nmol/L (normal, 190-630) and 580 +/- 60 nmol/L (normal, 50-410) at 0800 and 2000 h, respectively. Serum cortisol responded normally to insulin-induced hypoglycemia. Glucocorticoids and adrenal androgens were resistant to suppression by dexamethasone. The Kd of [3H]dexamethasone binding to the glucocorticoid receptors of mononuclear leukocytes was increased (6.4 +/- 0.8 nM; mean +/- SEM of four determinations; normal, 1.4-3.4; P less than 0.001), but the binding capacity was normal. This patient with isosexual precocity has PCR, as indicated by functionally abnormal glucocorticoid receptors and hypercortisolism without other clinical or biochemical manifestations of Cushing's syndrome. Excessive adrenal stimulation by ACTH caused increased secretion of both cortisol and adrenal androgens, and the latter caused the clinical manifestations. PCR should be considered in other male children with isosexual precocity or female children with heterosexual precocity.

Prediction of lactate threshold and fixed blood lactate concentrations from 3200-m time trial running performance in untrained females

The present study examined the effectiveness of a 3200-m time trial run for predicting VO2 and running velocity at lactate threshold (LT), and fixed blood lactate concentrations (FBLC) of 2.0, 2.5, and 4.0 mM and peak in untrained women. Thirty-nine female subjects completed a VO2peak/LT test a 3200-m time trial run. Twenty-eight subjects were randomly assigned to a validation sample and the remaining subjects were used for cross-validation purposes. In the validation sample, VO2 measurements at LT, FBLC of 2.0, 2.5, 4.0 mM, and peak were 22.5, 29.2, 31.2, 36.5, and 38.5 ml/kg.min-1, respectively. Velocities at LT, FBLC of 2.0, 2.5, 4.0 mM, and peak were 107.1, 129.7, 136.6, 155.1, and 163.2 m/min, respectively. Regression analysis in the validation group revealed that the 3200-m time trial was an accurate predictor of velocities at LT, FBLC of 2.0, 2.5, 4.0 mM, and peak with correlations of r = 0.70, r = 0.84, r = 0.85, r = 0.87, and r = 0.95, respectively, and standard errors of estimate ranging from +/- 9.5 m/min (for velocity peak) to +/- 13.7 m/min (velocity LT). Vor VO2 prediction, correlations ranged from r = 0.61 (3200-m time vs VO2 LT) to r = 0.77 (3200-m time vs VO2 peak) with the standard errors of estimate ranging from +/- 4.18 (VO2 2.0 mM) to +/- 4.87 ml/kg.min-1 (VO2 4.0 mM).(ABSTRACT TRUNCATED AT 250 WORDS)

Percentages of maximal heart rate, heart rate reserve, and VO2peak for determining endurance training intensity in sedentary women

The use of 60%-95% of maximal heart rate (HR max), heart rate reserve (HRR), and VO2peak as exercise training intensities was examined in sedentary women, and these intensities were related to HR and VO2 observed at the lactate threshold (LT) and fixed blood lactate concentrations of 2.0, 2.5, and 4.0 mM. Thirty-three subjects (means age = 32.5 +/- 3.9 yrs; means ht = 164.2 +2- 5.0 cm; means wt = 67.6 +/- 13.9 kg) completed a VO2/LT treadmill test using a level running protocol. The values at LT, 2.0, 2.5, 4.0 mM, and peak for VO2 were 22.3, 29.0, 31.0, 36.2, and 39.1 ml/kg.min-1, respectively; for velocity were 107.0, 128.9, 135.8, 152.8, and 164.4 m/min, respectively; and for HR were 142.1, 162.9, 169.4, 183.2, and 189.7 bts/min, respectively. The minimum intensity necessary for the majority of subjects to be above LT (n = 17) was 75% HR max while 90% HR max was required for the majority of subjects to be above 2.0 mM (n = 23) and 2.5 mM (n = 19). At 95% HR max 12 subjects were above 4.0 mM. For the majority of subjects to be above LT (n = 18), 55% HRR was necessary; 75%, 85%, and 95% HRR was required for the majority of subjects to be above 2.0 mM (n = 18), 2.5 mM (n = 19), and 4.0 mM (n = 20), respectively. For percent VO2peak, the intensities required for the majority of subjects to be above LT, 2.0 mM, 2.5 mM, and 4.0 mM were 55%, 75%, 80%, and 95% VO2peak, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphatidylinositol-glycan anchors of membrane proteins: potential precursors of insulin mediators

BC3H1 myocytes release membrane-bound alkaline phosphatase to the incubation medium upon stimulation with insulin, following a time course that is consistent with the generation of dimyristoylglycerol and the appearance of a putative insulin mediator in the extracellular medium. The use of specific blocking agents shows, however, that alkaline phosphatase release and dimyristoylglycerol production are independent processes and that the blockade of either event inhibits the production of insulin mediator. These experiments suggest a new model of insulin action.

Prediction of lactate threshold and fixed blood lactate concentrations from 3200-m running performance in male runners

To determine the effectiveness of a 3200-m time trial for predicting VO2 and running velocity at lactate threshold (LT), fixed blood lactate concentrations of 2.0, 2.5, and 4.0 mM, and peak, 42 male runners (means age = 31.1 +/- 8.3 years; means ht = 176.8 +/- 6.6 cm; means wt = 70.4 +/- 10.0 kg) completed a VO2 peak/LT test and a 3200-m time trial. The continuous treadmill protocol started at 0% grade 150 m/min and increased 10 m/min every 3 min until exhaustion. Velocity at LT, 2.0, 2.5, and 4.0 mM was determined from individual velocity blood lactate relationships, and VO2 values were determined from individual plots ov VO2 vs velocity. VO2 peak and velocity peak were chosen as the highest values observed. Oxygen uptake at LT, 2.0, 2.5, 4.0 mM, and peak was 52.51, 56.61, 58.31, 61.70, and 64.21 ml/kg.min-1, respectively, while the velocities associated with LT, 2.0, 2.5, 4.0 mM, and peak were 235.5, 251.5, 259.8, 273.5, and 285.5 m/min, respectively. During the 3200-m time trial (means time = 11.28 +/- 0.96 min), 400-m split times and cumulative times were recorded. Twenty-nine subjects were randomly assigned to a validation sample and the remaining subjects were used for cross-validation purposes. Regression analysis revealed that a 3200-m time trial was a good predictor of both VO2 (ml/kg.min-1) and velocity (m/min) at LT, 2.0, 2.5, 4.0 mM, and peak.

Apomorphine response and subtyping of schizophrenia

(1) We conducted a double-blind study of acute effects of low-dose apomorphine (0.01 mg/kg) in 12 chronic schizophrenic patients. (2) Overall, there was no significant difference in therapeutic response to apomorphine versus placebo. (3) Of the individual subscales of the Brief Psychiatric Rating Scale, anxiety and depression syndromes showed significant improvement with apomorphine. (4) On dividing the schizophrenic patients into two groups on the basis of computed tomography (CT) scans, it was found that there was a significant difference in their responsiveness to apomorphine. (5) Patients with abnormal CT scans (primarily, large ventricles) tended to have improvement or no change with apomorphine, whereas those with normal CT scans tended to have worsening of symptoms. (6) Possible implications of our findings are discussed.

Naloxone in chronic schizophrenic patients: neuroendocrine and behavioral effects

Naloxone produced improvement in abnormal thought content in medicated chronic schizophrenic patients, but not in drug-free patients. In contrast, drowsiness and increases in plasma prolactin concentrations were seen only in drug-free schizophrenic patients. Although growth hormone concentrations increased in drug-free and medicated schizophrenic patients, the time course was different in the two groups. Neuroleptics appear to alter naloxone's clinical and neuroendocrine effects in chronic schizophrenic patients.

Lymphocyte monoamine oxidase and plasma prolactin and growth hormone in tardive dyskinesia

Twelve elderly women with tardive dyskinesia were matched with 12 patients without dyskinesia. Lymphocyte monoamine oxidase (MAO) activity and plasma prolactin and growth hormone concentrations were determined "blind" in these 12 pairs of patients. Chronic schizophrenic patients with tardive dyskinesia had significantly lower lymphocyte MAO activity as compared to controls. Organic brain syndrome patients with dyskinesia did not differ from controls in the lymphocyte MAO activity. These results with lymphocyte MAO parallel our earlier findings on platelet MAO. No significant differences were found between dyskinesia group and controls in the plasma prolactin and growth hormone concentrations. Possible implications of our findings are discussed.

A correlation between platelet monoamine oxidase activity and plasma prolactin concentrations in man

Increases in plasma prolactin concentrations produced by alpha-methyl-p-tyrosine, a catecholamine synthesis inhibitor, varied inversely with baseline platelet monoamine oxidase activity in 12 patients with chronic schizophrenia. In normal volunteers with low monoamine oxidase activity and in unmedicated patients with chronic schizophrenia, plasma prolactin concentrations varied directly with platelet monoamine oxidase activity. No such relationship was found in normal subjects with high platelet monoamine oxidase activity. These data suggest that platelet monoamine oxidase activity reflects monoaminergic activity in the tubero-infundibular system, which in turn affects plasma prolactin concentrations. This relationship may be important in patients with low platelet monoamine oxidase activity, such as some chronic schizophrenics.

Possible effects of growth hormone on development of acute lymphoblastic leukaemia

Growth hormone (G.H.) or a G.H.-dependent somatomedin may be involved in the process of acute lymphoblastic leukaemia (A.L.L.). Growth hormone has a trophic effect on lymphoid tissue and also specific receptors on lymphocytes, most probably T cells. Hypophycess. Resting concentrations of G.H. and somatomedin activity are raised in some children with A.L.L. and may be reduced after remission is achieved. It is suggested that control of G.H. and/or somatomedin concentrations may be necessary for adequate treatment of some cases of A.L.L. in children.

Inhibition of dopamine synthesis in chronic schizophrenia. Clinical ineffectiveness of metyrosine

According to the dopamine (DA) hypothesis of schizophrenia, there is a functional excess of dopaminergic activity within unspecified areas of the brain in schizophrenic patients. As a clinical test of this hypothesis, we administered metyrosine for three weeks to symptomatic chronic male schizophrenic patients who were maintained on suboptimal doses of neuroleptic agents. Metyrosine inhibits tyrosine hydroxylase, the rate-limiting enzymatic step in the synthesis of DA. No clinical improvement was observed, using the National Institute of Mental Health Inpatient Behavioral Rating Scale or the Brief Psychiatric Rating Scale. Central inhibition of DA synthesis by metyrosine was suggested, however, by (1) the development of extrapyramidal side effects and (2) a significant increase in plasma prolactin concentrations. Plasma chlorpromazine concentrations remained unchanged during metyrosine treatment. There was, nevertheless, a significant improvement on the scores of the Wechsler Adult Intelligence Scale Comprehension subtest, which measures judgment and common sense. This finding suggests that DA may be involved in the regulation of subtle psychological processes. The results are discussed in light of the DA hypothesis of schizophrenia and previous reports suggesting that metyrosine potentiates the antipsychotic effect of neuroleptics in schizophrenia.